diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 44d234b0df5e..7705950ad70b 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1177,10 +1177,9 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
 		return -EINVAL;
 
 	/*
-	 * Enabling/disabling partition root is not allowed if there are
-	 * online children.
+	 * Enabling partition root is not allowed if there are online children.
 	 */
-	if ((cmd != partcmd_update) && css_has_online_children(&cpuset->css))
+	if ((cmd == partcmd_enable) && css_has_online_children(&cpuset->css))
 		return -EBUSY;
 
 	/*
@@ -1208,6 +1207,14 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
 		/*
 		 * partcmd_update with newmask:
 		 *
+		 * Make partition invalid if newmask isn't a subset of
+		 * (cpus_allowed | parent->effective_cpus).
+		 */
+		cpumask_or(tmp->addmask, cpuset->cpus_allowed,
+					 parent->effective_cpus);
+		part_error = !cpumask_subset(newmask, tmp->addmask);
+
+		/*
 		 * delmask = cpus_allowed & ~newmask & parent->subparts_cpus
 		 * addmask = newmask & parent->effective_cpus
 		 *		     & ~parent->subparts_cpus
@@ -1220,20 +1227,21 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
 		adding = cpumask_andnot(tmp->addmask, tmp->addmask,
 					parent->subparts_cpus);
 		/*
-		 * Return error if the new effective_cpus could become empty.
+		 * Make partition invalid if parent's effective_cpus could
+		 * become empty.
 		 */
 		if (adding &&
 		    cpumask_equal(parent->effective_cpus, tmp->addmask)) {
 			if (!deleting)
-				return -EINVAL;
+				part_error = true;
 			/*
 			 * As some of the CPUs in subparts_cpus might have
 			 * been offlined, we need to compute the real delmask
 			 * to confirm that.
 			 */
-			if (!cpumask_and(tmp->addmask, tmp->delmask,
-					 cpu_active_mask))
-				return -EINVAL;
+			else if (!cpumask_and(tmp->addmask, tmp->delmask,
+					      cpu_active_mask))
+				part_error = true;
 			cpumask_copy(tmp->addmask, parent->effective_cpus);
 		}
 	} else {
@@ -1242,19 +1250,23 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
 		 *
 		 * addmask = cpus_allowed & parent->effective_cpus
 		 *
+		 * This gets invoked either due to a hotplug event or
+		 * from update_cpumasks_hier() where we can't return an
+		 * error. This can cause a partition root to become invalid
+		 * in the case of a hotplug.
+		 *
 		 * Note that parent's subparts_cpus may have been
 		 * pre-shrunk in case there is a change in the cpu list.
 		 * So no deletion is needed.
 		 */
 		adding = cpumask_and(tmp->addmask, cpuset->cpus_allowed,
 				     parent->effective_cpus);
-		part_error = cpumask_equal(tmp->addmask,
-					   parent->effective_cpus);
+		part_error = (is_partition_root(cpuset) &&
+			      !parent->nr_subparts_cpus) ||
+			     cpumask_equal(tmp->addmask, parent->effective_cpus);
 	}
 
 	if (cmd == partcmd_update) {
-		int prev_prs = cpuset->partition_root_state;
-
 		/*
 		 * Check for possible transition between PRS_ENABLED
 		 * and PRS_ERROR.
@@ -1269,13 +1281,9 @@ static int update_parent_subparts_cpumask(struct cpuset *cpuset, int cmd,
 				new_prs = PRS_ENABLED;
 			break;
 		}
-		/*
-		 * Set part_error if previously in invalid state.
-		 */
-		part_error = (prev_prs == PRS_ERROR);
 	}
 
-	if (!part_error && (new_prs == PRS_ERROR))
+	if ((old_prs == PRS_ERROR) && (new_prs == PRS_ERROR))
 		return 0;	/* Nothing need to be done */
 
 	if (new_prs == PRS_ERROR) {
@@ -1407,6 +1415,11 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
 			case PRS_ENABLED:
 				if (update_parent_subparts_cpumask(cp, partcmd_update, NULL, tmp))
 					update_tasks_cpumask(parent);
+				/*
+				 * The cpuset partition_root_state may be
+				 * changed to PRS_ERROR. Capture it.
+				 */
+				new_prs = cp->partition_root_state;
 				break;
 
 			case PRS_ERROR:
@@ -1424,33 +1437,27 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp)
 
 		spin_lock_irq(&callback_lock);
 
-		cpumask_copy(cp->effective_cpus, tmp->new_cpus);
 		if (cp->nr_subparts_cpus && (new_prs != PRS_ENABLED)) {
+			/*
+			 * Put all active subparts_cpus back to effective_cpus.
+			 */
+			cpumask_or(tmp->new_cpus, tmp->new_cpus,
+				   cp->subparts_cpus);
+			cpumask_and(tmp->new_cpus, tmp->new_cpus,
+				    cpu_active_mask);
 			cp->nr_subparts_cpus = 0;
 			cpumask_clear(cp->subparts_cpus);
-		} else if (cp->nr_subparts_cpus) {
+		}
+
+		cpumask_copy(cp->effective_cpus, tmp->new_cpus);
+		if (cp->nr_subparts_cpus) {
 			/*
 			 * Make sure that effective_cpus & subparts_cpus
-			 * are mutually exclusive.
-			 *
-			 * In the unlikely event that effective_cpus
-			 * becomes empty. we clear cp->nr_subparts_cpus and
-			 * let its child partition roots to compete for
-			 * CPUs again.
+			 * of a partition root are mutually exclusive.
 			 */
 			cpumask_andnot(cp->effective_cpus, cp->effective_cpus,
 				       cp->subparts_cpus);
-			if (cpumask_empty(cp->effective_cpus)) {
-				cpumask_copy(cp->effective_cpus, tmp->new_cpus);
-				cpumask_clear(cp->subparts_cpus);
-				cp->nr_subparts_cpus = 0;
-			} else if (!cpumask_subset(cp->subparts_cpus,
-						   tmp->new_cpus)) {
-				cpumask_andnot(cp->subparts_cpus,
-					cp->subparts_cpus, tmp->new_cpus);
-				cp->nr_subparts_cpus
-					= cpumask_weight(cp->subparts_cpus);
-			}
+			WARN_ON_ONCE(cpumask_empty(cp->effective_cpus));
 		}
 
 		if (new_prs != old_prs)
@@ -1582,8 +1589,8 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
 	 * Make sure that subparts_cpus is a subset of cpus_allowed.
 	 */
 	if (cs->nr_subparts_cpus) {
-		cpumask_andnot(cs->subparts_cpus, cs->subparts_cpus,
-			       cs->cpus_allowed);
+		cpumask_and(cs->subparts_cpus, cs->subparts_cpus,
+			    cs->cpus_allowed);
 		cs->nr_subparts_cpus = cpumask_weight(cs->subparts_cpus);
 	}
 	spin_unlock_irq(&callback_lock);
@@ -2005,19 +2012,33 @@ static int update_prstate(struct cpuset *cs, int new_prs)
 		}
 	} else {
 		/*
-		 * Turning off partition root will clear the
-		 * CS_CPU_EXCLUSIVE bit.
+		 * Switch back to member is always allowed even if it
+		 * causes child partitions to become invalid.
 		 */
-		if (old_prs == PRS_ERROR) {
-			update_flag(CS_CPU_EXCLUSIVE, cs, 0);
-			err = 0;
-			goto out;
-		}
+		err = 0;
+		update_parent_subparts_cpumask(cs, partcmd_disable, NULL,
+					       &tmpmask);
+		/*
+		 * If there are child partitions, we have to make them invalid.
+		 */
+		if (unlikely(cs->nr_subparts_cpus)) {
+			struct tmpmasks tmp;
 
-		err = update_parent_subparts_cpumask(cs, partcmd_disable,
-						     NULL, &tmpmask);
-		if (err)
-			goto out;
+			spin_lock_irq(&callback_lock);
+			cs->nr_subparts_cpus = 0;
+			cpumask_clear(cs->subparts_cpus);
+			compute_effective_cpumask(cs->effective_cpus, cs, parent);
+			spin_unlock_irq(&callback_lock);
+
+			/*
+			 * If alloc_cpumasks() fails, we are running out
+			 * of memory and there isn't much we can do.
+			 */
+			if (!alloc_cpumasks(NULL, &tmp)) {
+				update_cpumasks_hier(cs, &tmp);
+				free_cpumasks(NULL, &tmp);
+			}
+		}
 
 		/* Turning off CS_CPU_EXCLUSIVE will not return error */
 		update_flag(CS_CPU_EXCLUSIVE, cs, 0);
@@ -3104,11 +3125,28 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
 
 	/*
 	 * In the unlikely event that a partition root has empty
-	 * effective_cpus or its parent becomes erroneous, we have to
-	 * transition it to the erroneous state.
+	 * effective_cpus, we will have to force any child partitions,
+	 * if present, to become invalid by setting nr_subparts_cpus to 0
+	 * without causing itself to become invalid.
+	 */
+	if (is_partition_root(cs) && cs->nr_subparts_cpus &&
+	    cpumask_empty(&new_cpus)) {
+		cs->nr_subparts_cpus = 0;
+		cpumask_clear(cs->subparts_cpus);
+		compute_effective_cpumask(&new_cpus, cs, parent);
+	}
+
+	/*
+	 * If empty effective_cpus or zero nr_subparts_cpus or its parent
+	 * becomes erroneous, we have to transition it to the erroneous state.
 	 */
 	if (is_partition_root(cs) && (cpumask_empty(&new_cpus) ||
-	   (parent->partition_root_state == PRS_ERROR))) {
+	    (parent->partition_root_state == PRS_ERROR) ||
+	    !parent->nr_subparts_cpus)) {
+		int old_prs;
+
+		update_parent_subparts_cpumask(cs, partcmd_disable,
+					       NULL, tmp);
 		if (cs->nr_subparts_cpus) {
 			spin_lock_irq(&callback_lock);
 			cs->nr_subparts_cpus = 0;
@@ -3117,38 +3155,23 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
 			compute_effective_cpumask(&new_cpus, cs, parent);
 		}
 
-		/*
-		 * If the effective_cpus is empty because the child
-		 * partitions take away all the CPUs, we can keep
-		 * the current partition and let the child partitions
-		 * fight for available CPUs.
-		 */
-		if ((parent->partition_root_state == PRS_ERROR) ||
-		     cpumask_empty(&new_cpus)) {
-			int old_prs;
-
-			update_parent_subparts_cpumask(cs, partcmd_disable,
-						       NULL, tmp);
-			old_prs = cs->partition_root_state;
-			if (old_prs != PRS_ERROR) {
-				spin_lock_irq(&callback_lock);
-				cs->partition_root_state = PRS_ERROR;
-				spin_unlock_irq(&callback_lock);
-				notify_partition_change(cs, old_prs, PRS_ERROR);
-			}
+		old_prs = cs->partition_root_state;
+		if (old_prs != PRS_ERROR) {
+			spin_lock_irq(&callback_lock);
+			cs->partition_root_state = PRS_ERROR;
+			spin_unlock_irq(&callback_lock);
+			notify_partition_change(cs, old_prs, PRS_ERROR);
 		}
 		cpuset_force_rebuild();
 	}
 
 	/*
 	 * On the other hand, an erroneous partition root may be transitioned
-	 * back to a regular one or a partition root with no CPU allocated
-	 * from the parent may change to erroneous.
+	 * back to a regular one.
 	 */
-	if (is_partition_root(parent) &&
-	   ((cs->partition_root_state == PRS_ERROR) ||
-	    !cpumask_intersects(&new_cpus, parent->subparts_cpus)) &&
-	     update_parent_subparts_cpumask(cs, partcmd_update, NULL, tmp))
+	else if (is_partition_root(parent) &&
+		(cs->partition_root_state == PRS_ERROR) &&
+		 update_parent_subparts_cpumask(cs, partcmd_update, NULL, tmp))
 		cpuset_force_rebuild();
 
 update_tasks:
